PROJECT SUMMARY ? SIMONICH/SEMPRINI PROJECT Although remediation and detection research projects funded by the NIEHS Superfund Research Program have saved >$100 million, recent studies by our laboratory and others have shown that the toxicity of PAH- contaminated soils and sediments increases after biotic and abiotic remediation and that PAH primary transformation products can account for only 23-28% of the increased toxicity. Polar secondary PAH transformation products (e.g., epoxides, carbonyls, and ring-cleavage products) likely account for the majority of toxicity increase after remediation. The overarching goal of this project is to learn to identify remediation technologies that minimize formation of hazardous PAH breakdown products. Our first specific aim is to predict, via computational modeling, the secondary transformation products of PAHs that will form during biotic (microbial) and abiotic (with heat or in situ chemical oxidation) remediation. Our second specific aim is to measure the secondary PAH transformation products that form during laboratory-scale biotic and abiotic remediation experiments. We will feed back our data into Aim 1 to refine our computational model. Our third specific aim is to measure the secondary transformation products of PAHs in real-world Superfund soils and sediments before and after remediation, as well as after natural attenuation. Our fourth specific aim is a) to identify remediation technologies, or combinations of remediation technologies, that minimize the formation of toxic primary and secondary transformation products of PAHs and b) to understand how the optimal remediation strategy depends on the remediation conditions and on the properties of the soils and sediments. We also plan to test any new remediation technologies our stakeholders, or other SRP Centers, wish to evaluate. We will apply passive sampling devices to assess the bioavailability of PAHs and their transformation products. We also apply soil column leaching techniques to assess their tendency to leach from to soil to groundwater. These four Specific Aims, taken together, will help us answer our stakeholders' questions regarding which PAH-transformation products at Superfund sites are hazardous, which transformation products have the potential to result in human exposure, and which exposures have the potential to compromise human health. Based on our findings, we will advise the managers of specific Superfund sites regarding which remediation strategies (or combinations of strategies) minimize the threat to society.